Prevalence and predictors of anemia among six-week-old infants in Kwale County, Kenya: A cross-sectional study

Anemia is a significant public health problem among children worldwide. The etiology of anemia is multifactorial but iron deficiency (ID) is the most common cause of anemia in low- and middle-income countries. ID and anemia in infancy can impair growth and cognitive development. The aim of this study was to determine the prevalence and predictors of anemia among six-week-old infants in Kwale County, Kenya. This cross-sectional study included 424 mother-infant pairs. Structured questionnaires were administered to the mothers to obtain information on socio-demographic variables, maternal characteristics and birth information. Anthropometric data was collected for each child. A heel prick was done to measure hemoglobin and zinc protoporphyrin concentration levels. Chi-square test, bivariate and multivariate regression analyses were done to determine factors associated with anemia. The prevalence of ID, anemia and IDA was 60.4% (95%CI: 55.9–65.2), 21.0% (95%CI: 17.5–25.2) and 15.8% (95%CI: 12.7–19.7) respectively. Bivariate analysis showed that the risk of anemia was significantly higher among male infants (odds ratio (OR) = 2.20 (95%CI: 1.33–3.63), p = 0.002), iron deficient infants (OR = 2.35 (95%CI: 1.39–3.99), p = 0.001) and infants from Msambweni Sub-County (OR = 2.80 (95%CI: 1.40–4.62), p<0.001). Multivariate analysis revealed that odds of anemia were significantly higher in infants born to mothers who did not use iron supplements during pregnancy (adjusted odds ratio (aOR) = 74.01 (95%CI: 2.45–2238.21), p = 0.013 and significantly lower in infants born to mothers with parity ≥ 4 (aOR = 0.05 ((95%CI: 0.00–0.77), p = 0.024). In six-week-old infants in rural Kenya, anemia prevalence was 21.0% with ID accounting for 75.3% of anemia cases. Given the physical and cognitive impairments associated with ID and anemia in early infancy, it may be prudent to re-evaluate the current Kenyan pediatric protocols to include anemia screening and potential treatment of infants less than 6-months of age.


Conclusion
In six-week-old infants in rural southern Kenya, anemia prevalence was 21.0% with ID accounting for 75.3% of anemia cases.Current Kenyan pediatric protocols specify provision of iron to anemic infants older than 6 months of age.Given the physical and cognitive impairments associated with ID and anemia in early infancy, it may be prudent to re-evaluate these pediatric protocols to include anemia screening and potential treatment of infants less than 6-months of age.This statement will be typeset if the manuscript is accepted for publication.
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This was a cross-sectional study among six-week-old infants including 424 mother-infant pairs.
Structured questionnaires were administered to the mothers of the infants to obtain information on socio-demographic characteristics, maternal and birth information.Anthropometric data was collected for each child.A heel prick was done to measure hemoglobin and zinc protoporphyrin concentration using point-of-care devices.Prevalence of key nutritional conditions was done using binomial regression models.Chi-square was done to determine association between key variables.Univariable and multivariable regression analysis were done to determine factors associated with anemia.A spatial heat map was developed to show the spatial distribution of anemia cases in Kwale County.

Results:
The overall prevalence of ID, anemia and IDA among infants in Kwale county was 60.4% (95%CI: 55.9-65.were all significantly associated with infant anemia status.

Conclusion:
In six-week-old infants in rural southern Kenya, anemia prevalence was 21.0% with ID accounting for 75.3% of anemia cases.Current Kenyan pediatric protocols specify provision of iron to anemic infants older than 6 months of age.Given the physical and cognitive impairments associated with ID and anemia in early infancy, it may be prudent to re-evaluate these pediatric protocols to include anemia screening and potential treatment of infants less than 6-months of age.

Introduction
Anemia continues to be a significant public health problem in the world affecting over a third of the global population with a worldwide prevalence of 22.8% across all ages (Gardner & Kassebaum, 2020) causing 68 million disability adjusted life years (DALYS) [2] .The World Health Organization (WHO) estimates that 42% of children < 5 years of age and 40% of pregnant women worldwide are anemic while one-third of all reproductive age women are anemic (WHO, 2022).Regional estimates show that Sub-Saharan Africa bears the highest burden of anemia with a prevalence of 62% followed by South-East Asia (53%) while the Western pacific region has the lowest prevalence (21.9%) (WHO, 2022).Children under five years have the highest burden of anemia, predominantly in low-and middle-income countries (LMIC) and more often it's due to ID as the most implicated cause accounting for ≥60% of the cases of anemia [2].In Sub-Saharan Africa anemia is already common in infants < 1 year of age, as early as at the time of routine vaccination; e.g., 70% of 6-month-old infants in south coastal Kenya are anemic [4].
Anemia of any etiology is associated with increased risks for child mortality and morbidity [5].
More specifically, iron deficiency anemia (IDA) in early infancy may result to irreversible cognitive development and cause physical retardation in growth [6].Iron deficiency (ID) may also impair adaptive immunity and thereby reduce efficacy of vaccines in early infancy although the data on this is scanty and the immunology of malnutrition is not well understood [7][8].As a result, IDA reduces the productivity of these infants as they grow through adolescence into adulthood since they have impaired cognitive ability and reduced physical development [9].Other risk factors associated with anemia in the developing countries include: genetically acquired traits such as thalassemia and hemoglobinopathies, hemolysis or blood loss due to parasitic infections especially in malaria endemic areas, and other nutritional deficiencies including folate deficiency and vitamins A, C and B12 deficiencies [10].
Additionally, postnatal factors including frequent illnesses like pneumonia, earlier introduction of low iron content cereal-based complimentary foods, rapid postnatal growth rate, low birth weight as well as infectious diseases like malaria predispose infants to an early onset of ID state regardless of whether they were born at term or not [11].
In Kenya the nationwide prevalence of anemia in children under one year has been reported to be 39.5% [12].Another study among infants 6 to 9 months in Keiyo sub-County found anemia prevalence to be 21.7% [13].A study in Kwale County among infants aged 3-6months found the prevalence of ID, anemia and IDA to be 69%,52% and 38% respectively (Mikulic et al., 2020); but the study was small and non-representative.
Early infancy provides the window of opportunity for various health interventions such as routine childhood immunization beyond which such interventions may not work and may result re-emergence of vaccine preventable diseases, poor growth as well as cognitive impairment with possible future health problems that may be irreversible [15][16].In addition, ID may also be a previously unrecognized contributor to the reduced efficacy of vaccines in Sub-Saharan Africa [8].Given these highlights, it is important to evaluate the role of anemia in early infancy as a contributor to high child mortality and morbidity in Sub-Saharan Africa.
Provision of iron supplements to infants and children 6-24 months of age has been recommended in areas where anemia is a severe public health problem i.e., prevalence ≥40 % (WHO, 2016).However, infants below six months of age have been exempted from many recommendations targeting prevention and treatment of ID and anemia in highly prevalent anemia regions.This is because it has generally been assumed that infants during their first six months of life are protected from IDA because they have accumulated adequate body iron stores during fetal life and therefore anemia is not a problem at this age [18].However, this may not be the case in sub-Saharan Africa because sufficient iron is passed from the mother to the fetus only if the mother has adequate iron stores during pregnancy and most pregnant women in their third trimester in Africa are anemic and iron deficient [2].Although delayed cord clamping has recently been proposed to prevent ID and the resulting anemia in infants, it has been difficult to implement in sub-Saharan Africa because of weak healthcare systems and busy maternity wards [19].
Despite all our knowledge on anemia and ID in children, researchers point out that there is much that remains unknown about this problem in early infancy.Previous studies on anemia in Kenya have been restricted to infants above six months of age (Ngesa & Mwambi, 2014;Onyangore et al., 2016;Jaeggi et al., 2013).Moreover, prior studies on anemia in malaria endemic regions in LMIC who have the highest burden of anemia in younger children have not included geographical factors in assessing the relationships between such outcomes and ecological as well as geographic factors [20].The aim of this study therefore, was to determine the prevalence of anemia and ID with associated predictors among six-week-old infants in Kwale County, Kenya with a global aim of improving infants' nutritional status in early life.

Study design and setting
This

Sample size determination
Sample size was calculated using Fisher et al formula (1998); n=(z 2 pq)/e 2 ; where Z is the value from standard normal distribution corresponding to 95% confidence level (Z=1.96),p is the estimated prevalence of anemia among infants in Kwale County (assumed as 50%), q is the proportion of infants without anemia (1-p), e is the margin of error assumed as 5%.The final sample size was thus calculated as 424 mother-infant pairs after factoring in a 10% nonresponse rate.Simple random sampling was used to select the final sample size from the total number of mother-infant pairs who were eligible to be enrolled in the study.The participants were randomly sampled from the number of mother-infant pairs that came for screening for the RCT.

Survey procedures
The study was carried out between January and April 2023.During recruitment, the study purpose was explained to the mothers and those who were willing to participate were scheduled for a screening date at the hospital when their child would be exactly 6 weeks old ± 3 days.On the day of screening, the study aim was explained again in detail to the mothers who signed consent forms both in English and Swahili and each mother-infant pair given a unique identification number.A screening form was programmed onto redcap and administered using tablets.The study included HIV negative mothers above 15 years of age with infant aged 6 weeks ± 3 days, born via vaginal delivery, full-time breastfed, not having received any vaccine beyond the birth dose of Oral Polio Vaccine (OPV) and Bacillus Calmette-Guerin (BCG), and with no medical condition that precludes study involvement.The study excluded infants with conditions that might have affected participation such as hematological and non-hematological malignancies, chronic kidney disease, diabetes and inability to provide maternal informed consent.Mother-infant pairs who met the inclusion criteria were enrolled into the study.

Data collection
An

Data management and analysis
The WHO anthropometrics software was used to calculate infants Z-scores for weight for length (WLZ)-wasting, weight for age (WAZ)-underweight and length for age (LAZ)-stunting.
Both questionnaires and laboratory diary information were programmed into tablets then used to capture data electronically on Redcap which had inbuilt data quality checks to reduce errors during the data entry process.Collected data was sent to the server daily.At the end of the data collection period, all data was downloaded onto MS Excel then transported to Stata version 16 for analysis.Descriptive analysis was done to describe characteristics of the participants.
Summary tables were used to show proportion of infants with selected nutritional conditions such as wasted, underweight, stunted, ID, anemic and those with IDA by different factors.Chi square test was used to show association between predictor variables and anemia status.
Both maternal and infant factors related to anemia were analyzed on univariable analysis and strength of association reported as odds ratio (OR) with 95% confidence intervals (CI).
Variable multicollinearity was done to identify variables that were strongly correlated.To select variables for multivariable analysis an inclusion criterion of p-value <0.5 was used in a stepwise variable selection method.A multivariable analysis was done using the selected variables and strength of association reported as adjusted OR (aOR) with 95% CI.Sub-County, ward (location) and village of residence of the infants in the study was be displayed on spatial heat map to show the spatial distribution of anemia cases in Kwale County.

Ethical approval and consent to participate
Approval for the study was sought from the JKUAT Institutional Ethics review Committee (approval number; JKU/IERC/02316/0052).Additional approval was provided by the Kwale county health authorities after they were appropriately briefed about the study.At the facility level written participant consent was obtained from the mothers.1).

Sociodemographic characteristics of participants
All infants in the study were aged 6 weeks (± 3 days) old.55% of the infants were male while 45% were female.The mean birth weight of the infants was 3.10 kg (SD=0.5kgs)ranging from 2.0 kg to 5.0 kg.Mean weight of the infants at the six weeks was 4.7 kg (SD=0.6kgs)and mean height was 54.7 cm (SD=2.1cm).Mean head circumference was 37.9 cm (SD=1.6cm)and average gestation weeks at birth was 37 weeks (SD= 1 week).Mean Hb

Chi square analysis of factors associated with anaemia
Infants from Msambweni Sub-County had a significantly higher prevalence of anemia (  2 = 17.0, df=1, p<0.001) compared to infants from Matuga Sub-County.
Mothers who did not use iron supplements during pregnancy had marginally non-significant higher odds of having infants with anemia than mothers who used iron supplements during pregnancy, OR=9.0 (95%CI:0.79-102.8,p=0.077) (Table 4).

Multivariable analysis of factors associated with anaemia
Pairwise correlation of variables in the univariable analysis was used to assess for correlation (Table 5).Stepwise variable selection with an inclusion criterion of p-value<0.5 was then done which included variables such as parity, birthweight, gender, age of the mother, use of iron supplements, education level and iron deficiency in the multivariable analysis model.

Discussion
This study examined 424 mother-infant pairs of six-week-old infants and found the prevalence of anemia, ID and IDA to be 21.0%,60.4% and 15.8% respectively.Significant factors associated with anemia on univariable analysis were infants iron deficiency status, gender, mothers use of iron supplements during pregnancy and the sub-County of residence.
On multivariable analysis, factors that remained significant were only two; use of iron supplements during pregnancy and parity of ≥4; possibly because of low anemia prevalence.
Anemia prevalence in this study is slightly lower than the global anemia prevalence of 22.8% across all ages (Gardner & Kassebaum, 2020) and 42% in children < 5 years of age [3].
Similarly, anemia prevalence in this study is lower than the prevalence in older Kenyan infants where 70% of infants at 6-months of age are anemic [4] and the nationwide anemia prevalence in Kenyan children under one year of 39.5% [12].In addition, this prevalence is also lower compared to a prevalence of 69% in a recent non-representative study in the same area of Kenya among infants aged 6-10 months (Nyilima et al 2021).This is not surprising as younger infants are generally have high Hb levels in the first few weeks after birth due to high levels of circulating fetal hemoglobin (HbF); these levels decrease progressively over the first 6-months as HbF is replaced by adult hemoglobin (HbA) [23].According to WHO categorization of anemia the 21.0% anemia prevalence is of moderate public health significance and therefore it is important to reduce this burden to be of mild or of no public health significance (World Health Organization, 2016).
Prevalence of ID and IDA in this study was 60.4% and 15.8% respectively.This means ID accounted for 75.3% of the total anemia cases in this study.This agrees with documented global anemia burden where ID accounted for ≥60% of the cases of anemia in children <5 years in LMIC who predominantly have the highest burden of anemia [2].A previous study among infants aged 3-6months in Kwale County found the prevalence of ID and IDA to be 69% and 38% respectively (Mikulic et al., 2020); but the study was small and non-representative.IDA in early infancy may result to irreversible cognitive development and cause physical retardation in growth [6].In addition, ID not only causes anemia but may also impair adaptive immunity and thereby reduce efficacy of vaccines in early infancy although the data on this is scanty and the immunology of malnutrition is not well understood [7][8].
Infant gender significantly predicted anemia status with male infants having an increased risk of anemia compared to female infants.Few studies have been done to address the question of gender differences on anemia and iron status in early infancy.Some studies have found higher anemia prevalence in boys compared to girls (61.3%) [24] [4].These differences reflect increased cases of true ID state in boys while others point to genetics [25].Anemia in infancy is associated with alterations in systemic metabolism dependent on gender with male infants having higher prevalence of anemia and ID due to greater oxidative stress and microbial dysfunction compared to female infants [26].
Iron supplementation in this study significantly predicted infants' anemia status with infants born of mothers who reported to have not used iron supplements during pregnancy having an increased risk of anemia compared to infants born of mothers who reported to have used iron supplements during pregnancy.This is in agreement with other clinical trials studies on effect of daily iron supplementation in conjunction with folic acid and other vitamins and minerals for pregnant women as an intervention in antenatal care, which showed that supplementation with iron reduced the risk of ID and maternal anemia [27].During pregnancy, iron supplementation produces more benefits to both the mother and the baby by promoting fetal health, preparing the fetus with adequate iron stores to be used during early postnatal stages of life as well as reducing maternal morbidity (Georgieff et al., 2019).
In this study infants in Msambweni Sub-County had significantly higher risk of anemia compared to infants in Matuga Sub-County.While there was no direct measure of diet or other factors leading to this, this may be because of disparities in socio-economic status, healthseeking behaviors, access to health and nutrition literacy within Kwale County.
In this study infants of mothers with parity of four or more were significantly less likely to be anemic compared to infants born of mothers of parity one.This is in contrast to other studies where maternal parity has also been shown to be associated with childhood anemia with prevalence increasing as maternal parity increases [24].However, these studies examined older infants from ages 6 months and older whereby many children in the family impacts the ability to feed them appropriately.The contrast in our study could be because mothers who have more than one child are more likely to comply and adhere to the importance of using iron supplements given during pregnancy through education and sensitization in previous pregnancies from health experts.
Whilst our study did not show any significant association between gestational age, birth weight and maternal anemia with infants' anemia status, other studies have shown significant associations.Preterm and low birthweight infants at a higher risk of developing ID and IDA because of higher iron requirements compared to term and normal birth weight infants due to increased post-natal growth rate [29].A study in Bangladesh found significant association between maternal anemia and occurrence of childhood anemia with anemia prevalence among children born of anemic mothers being higher (62%) compared to children born of non-anemic mothers [30].

Study strengths and limitations
Major strength of this study was that it was population based as infants were recruited from villages surrounding the hospitals, maternity wards, well-baby clinics and vaccination clinics and therefore is likely more representative of the study area population.Hemocue 301 system device used in this study to determine anemia status is highly reliable and used routinely in clinical practice.The iCheck Anemia device (Bioanalyt, Germany) used in this study to determine ID status has been shown to be useful in screening for ID in field surveys especially in children because its measurement can be done directly with a single drop of disclosure statement that describes the sources of funding for the work included in this submission and the role the funder(s) played.This includes grants and any commercial funding of the work or authors.
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was a cross-sectional study conducted in Msambweni County Referral Hospital and Kwale Sub-County Hospital in Kwale County.The study was nested within a randomized clinical trial (RCT)(ref).The primary objective of the RCT was to determine whether detecting and correcting ID and IDA using well absorbed iron improves efficacy of vaccines and to define the specific immune mechanisms underlying this effect.Kwale County is located in south coast of Kenya at Coordinates: 4°10′S 39°27′E bordering the Republic of Tanzania to the South West, Indian Ocean to the East, Taita-Taveta County to the West, Kilifi County to the North and Mombasa County to the North East.It has an estimated population of 866,820 (KNBS, 2019).Msambweni County Referral Hospital is a Level 5 government health facility.It offers both inpatient and outpatient medical services and has a bed capacity of 155.Being a referral hospital, it receives several cases from different areas within the county and therefore a good representative of the county population.Kwale Sub-County Hospital is a high-volume level 4 government health facility within Matuga Sub-County.It has a bed capacity of 62 and offers both inpatient and outpatient medical services.
, GES: Gestational weeks, PAR: Parity, BW: Birth weight, GEN: Gender, IDA: Iron deficient anemia, WAS: Wasting, UWT: Underweight, STU: Stunted, AMO: Anemic mother, UIS: Use of iron supplements, AGM: Age of the mother, WOM: Weight of the mother, EDS: Education level, WOC: Weight of the child, HOC: Height of the child, HCC: Head circumference of the child.
concentration of the infants was 12.3g/dl (SD=1.5g/dl).Mean ZnPP concentration of the infants was 44.0µmol/mol Hb (SD=13.1µmol/molHb).Mean age of mothers in the study was 27.7 years (SD=6.1 years).Mean weight of the mothers was 59.8 kg (SD= 12.3 kg).The median number of children per mother was 3 with a minimum of 1 child and a maximum of 11 children.Mean Hb concentration of the mothers during the last ANC visit was 10.8 g/dl (SD=1.4g/dl).Maternal information on education level and use of iron supplements during pregnancy was available for 157 mothers of whom 98.1% reported to having used iron supplements during pregnancy while 2% reported to not have used iron supplements during pregnancy.Mothers who had attained post-secondary level of education were 17.8%, those with secondary education level were 21.7%, those with primary education level were 54.1% and those with no education level were 6.4%.

Table 1 :
Socio-demographic and health information of the mothers and infants surveyed in Kwale County, Kenya

Table 2 :
Proportion of infants with selected nutritional conditions

Table 3 :
Chi-square association of anaemia with selected predictors among six-week-old infants in Kwale County, Kenya.

Table 4 :
Univariable logistic regression analysis of factors associated with anemia among six-week-old infants in Kwale County, Kenya.

Table 5 :
Pairwise correlation of factors associated with anemia among six-week-old infants in Kwale County, Kenya

Table 6 :
Multivariable logistic regression analysis of factors associated with anemia among six-week-old infants in Kwale County, Kenya